1. Field of the Invention
The present invention relates to a method of fabricating a photo mask for an organic light emitting display and, more particularly, to a method of fabricating a photo mask for an organic light emitting display so as to prevent deterioration of display quality, such as a horizontal line-shaped spot generated by the influence of critical dimension (CD) dispersion, and a photo mask so fabricated.
2. Description of the Related Art
Recently, flat panel displays (FPD) capable of reducing weight and volume of cathode ray tubes (CRT) so that they are made small and light are being spotlighted. The FPDs include a liquid crystal display (LCD), an organic light emitting display, a field emitter display (FED), and a plasma display panel (PDP).
Among the FPDs, the organic light emitting display has a wider range of usage temperature, is more resistant to shock or vibration, and has a larger view angle and higher response speed than the other FPDs so as to provide a clean moving picture, and thus the organic light emitting display is spotlighted as a next generation FPD.
The organic light emitting display is a display using a phenomenon in which electrons injected into an organic thin film through a negative electrode, and a negative electrode and holes, are recombined with each other to form exciton, and light of a specific wavelength is generated from the formed exciton. Since the organic light emitting display includes emission elements, an additional light source is not required, unlike in the LCD, and the brightness of organic light emitting diodes (OLED) which constitute the organic light emitting display is controlled by the amount of current that flows in the OLEDs.
To be specific, in the LCD, a desired data voltage is to be applied in a period where scan signals are applied in a voltage driving method. However, in the organic light emitting display, current that flows to the OLEDs of pixels is to be uniformly maintained so that the screen generated by a previous frame is displayed before the previous frame changes into a next frame.
That is, since the brightness of the organic light emitting display is controlled by the amount of current that flows to the OLEDs, precise deposition processes are required to be performed in forming the pixels.
The pixels of the organic light emitting display include various elements, such as a transistor and a capacitor, which are formed by a deposition process using a shadow mask or a fine metal mask (FMM).
In this case, due to the influence of the critical dimension (CD) dispersion generated when the deposition process is performed by the photo mask, a slight difference between the capacities of the capacitors of the pixels may be generated.
For example, in the case of the capacitors formed on the scan lines in pixel regions, respectively, a horizontal line-shaped spot is generated in accordance with the CD dispersion generated when the electrodes of the capacitors are formed.
Due to the characteristics of the organic light emitting display, in order to reduce the influence of the CD dispersion of the photo mask used for processes of fabricating the organic light emitting display, a method of reducing the tolerance of the photo mask, that is, of precisely fabricating the photo mask, is required.